Twenty-seven Catholics charge in a lawsuit that they were abused by priests as children and that the Diocese of Brooklyn covered up the abuse in line with secret Vatican policy.

The $300 million lawsuit, filed yesterday in Queens Supreme Court, charges the diocese with a “well-organized, successful and corrupt” cover-up scheme.

That scheme was authorized by a secret 1962 Vatican document, said lawyer Michael Dowd, who brought the suit.

The document – uncovered by lawyers investigating church sex abuse around the country – says those who handle allegations of priestly sex abuse are “restrained by a perpetual silence” enforceable by “penalty of excommunication.”

“That’s a bombshell of a document,” said Dowd.

Although Dowd and other lawyers pursuing sex cases against the church see the document as a smoking gun, some in the church say it has been misinterpreted.

In any case, it could be key to the new lawsuit because Dowd cites the cover-up to get around state law that says allegations of child-sex abuse generally should be brought to court before a victim reaches age 21.

The lawsuit explains: “The principal purpose of this successful scheme was to deprive plaintiffs of the facts necessary to establish claims against the diocese, the bishops and their subordinates for misconduct until the applicable statutes of limitations had expired and thereafter.”

Dowd said, “We are saying that the church defrauded these plaintiffs.”

He is appealing the dismissal of a similar lawsuit he filed in Queens last year on behalf of 42 plaintiffs. A judge ruled that lawsuit was filed too late because the plaintiffs were over age 21.

Some of the 24 priests named in yesterday’s suit are still working in parishes, Dowd said.

“These are horrific cases of abuse, lasting in some cases eight years, involving violence, sodomy – almost every kind of deviant sexual activity you could imagine,” he said.

A diocese spokesman declined comment on the lawsuit, saying it had not received the papers yet.